Header Question...

[Catnip]

Does the megaphone design where it goes from 2.5" to 3" make a noticeable difference from lets say just straight 2.5" to 2.5" exhaust or 2.5" to a flange, then a regular "reducer" flipped around to go to 3"?

If that makes sense.



Also, do the longer largest primaries add performance?



*waits for Mike*

[Vteckidd]

The number one thing IMO is primary length and size. Collector, megaphone, reverse megaphone etc helps tweak power but it's mainly decided by primary size and length.

Bigger always isn't better, you want exhaust to be pulled out with velocity and not be choked , etc

IMO 1 7/8ths work well, stepped is even better if you can do it, burns style collector seem to be the besT

[thundercatz1]

damn that header looks good

[Catnip]

The number one thing IMO is primary length and size. Collector, megaphone, reverse megaphone etc helps tweak power but it's mainly decided by primary size and length.

Bigger always isn't better, you want exhaust to be pulled out with velocity and not be choked , etc

IMO 1 7/8ths work well, stepped is even better if you can do it, burns style collector seem to be the besT

EXACTLY what I was looking for! Thanks for posting up, man.

[Jenson]

What your asking is do the High Velocity Merge Collectors help. Yes they help scavanging a good bit, in a comparison we did on an engine dyno we saw a 5Hp gain across the board and 7 peak using a burns HVMC (no spike) versus a standard stamped 4 into 1. This was on a 10.0:1/CR 2.3L. As Mike said, primary length and size are the biggest part, but I believe that the way the header comes off the head plays an important role too. Its just a theory of mine, one day I'll be able to test it on the flow bench. Like your second picture posted, that comes off the head very nicely. You dont want to just go 90 degrees out the head. The larger primaries are required once you start moving more air like going up in displacement.

[Catnip]

What your asking is do the High Velocity Merge Collectors help. Yes they help scavanging a good bit, in a comparison we did on an engine dyno we saw a 5Hp gain across the board and 7 peak using a burns HVMC (no spike) versus a standard stamped 4 into 1. This was on a 10.0:1/CR 2.3L. As Mike said, primary length and size are the biggest part, but I believe that the way the header comes off the head plays an important role too. Its just a theory of mine, one day I'll be able to test it on the flow bench. Like your second picture posted, that comes off the head very nicely. You dont want to just go 90 degrees out the head. The larger primaries are required once you start moving more air like going up in displacement.

I'm thinking about just modifying my DC 4-2-1, with longer primaries (I have no A/C, so the space is there) and then adding a megaphone and reverse cone. I'll be making the megaphone/reverse cone and just using 1 7/8" piping from the flange to the existing primaries. With the "stock" primaries flared to where the 1 7/8" pipe from the flange, will slide in, the transition shouldn't be choppy and pretty smooth.

Obviously, this it just until I can get a real header or at least a decent one, but I don't want to do random things that aren't at least good ideas... lol

[Vteckidd]

What your asking is do the High Velocity Merge Collectors help. Yes they help scavanging a good bit, in a comparison we did on an engine dyno we saw a 5Hp gain across the board and 7 peak using a burns HVMC (no spike) versus a standard stamped 4 into 1. This was on a 10.0:1/CR 2.3L. As Mike said, primary length and size are the biggest part, but I believe that the way the header comes off the head plays an important role too. Its just a theory of mine, one day I'll be able to test it on the flow bench. Like your second picture posted, that comes off the head very nicely. You dont want to just go 90 degrees out the head. The larger primaries are required once you start moving more air like going up in displacement.

Jenson prob has way more experience in this area than i do as well as Chunky on here too so you may want to get more in depth answers from them.

Jenson is right, the angle off the head is very important too. IMO its all about carrying the velocity out of the head through the primaries to the exhaust. The collector certainly makes a difference, but i think the "power" is well decided before then.

[Vteckidd]

I'm thinking about just modifying my DC 4-2-1, with longer primaries (I have no A/C, so the space is there) and then adding a megaphone and reverse cone. I'll be making the megaphone/reverse cone and just using 1 7/8" piping from the flange to the existing primaries. With the "stock" primaries flared to where the 1 7/8" pipe from the flange, will slide in, the transition shouldn't be choppy and pretty smooth.

Obviously, this it just until I can get a real header or at least a decent one, but I don't want to do random things that aren't at least good ideas... lol

What size are the primaries on the DC USDM? they should be close to 1 7/8th almost all B series headers nowadays are close to that or 1.75in etc bloh blahb blah

You would be surprised how much a 2.5in collector makes. Chop off the last 8in of your USDM header and weld in a 2.5in pipe like my Narrow header and youll see good gains.

[Catnip]

What size are the primaries on the DC USDM? they should be close to 1 7/8th almost all B series headers nowadays are close to that or 1.75in etc bloh blahb blah

You would be surprised how much a 2.5in collector makes. Chop off the last 8in of your USDM header and weld in a 2.5in pipe like my Narrow header and youll see good gains.

I think you're right on the size, although I haven't measured for sure. I already did the 2.5" collector mod, but I can see how it could be improved... especially if I'm going B20 bottom end.

[Jenson]

I think the DC's are 1-3/4 IIRC. So you want to go with a 1-3/4 stepped to 1-7/8, straight out of the head like the one pictured, standard 2.5" collecter with reverse cone and megaphone? Sounds good in theory imo. The only thing you will lose if you go straight 1-7/8 will be a little low end, if your not worried about that then dont waste your time. If your only reving to 7K you may not fully benefit from the 1-7/8 though

[Catnip]

I think the DC's are 1-3/4 IIRC. So you want to go with a 1-3/4 stepped to 1-7/8, straight out of the head like the one pictured, standard 2.5" collecter with reverse cone and megaphone? Sounds good in theory imo. The only thing you will lose if you go straight 1-7/8 will be a little low end, if your not worried about that then dont waste your time. If your only reving to 7K you may not fully benefit from the 1-7/8 though

I didn't get a Honda to have bottom end power, lol. That's what I don't understand about people. (I understand you were warning me, lol)

But if you both think it sounds good in theory, I might go ahead and try it on the DC. I have nothing to lose, because if it works good, I don't have to buy another header, but if it doesn't, I was planning to buy another better one.

[Jenson]

I say do it.

Your hatch looks just like mine, only yours doesnt have dents everywhere lol. Flat black EH2 for life!